This invention relates generally to head design for an optical data storage system. More particularly, the present invention relates to a flying head assembly carrying e.g., a solid immersion lens having a light-beam mesa surrounded by a thin film electromagnetic coil and a field enhancing pole structure for concentrating the electromagnetic flux from the coil toward an underlying storage location of a magneto-optical storage medium over which the flying head assembly is passing for data storage and retrieval. The pole structure may also perform a thermal spreading function in order to remove heat from the mesa and coil, and medium adjacent thereto.
New optical recording technologies, such as near field recording, require that an optical element, such as a solid immersion lens (xe2x80x9cSILxe2x80x9d), present an optical aperture in very close proximity to an optical medium. Accordingly, placing the SIL onto a slider body which flies above a storage medium upon an air bearing achieves desired proximity. Examples of air bearing slider bodies are provided by U.S. Pat. No. 5,497,359 to Mamin et al., entitled: xe2x80x9cOptical Disk Data Storage System with Radiation-Transparent Air-Bearing Sliderxe2x80x9d, and U.S. Pat. No. 5,729,393 to Lee et al., entitled: xe2x80x9cOptical Flying Head with Solid Immersion Lens having Raised Central Surface Facing Mediumxe2x80x9d, the disclosures thereof being incorporated herein by reference.
Rewritable optical storage may be implemented with phase change media, and it may be implemented with magneto-optical (xe2x80x9cMOxe2x80x9d) media. In the case of MO media a recording layer presents very stable magnetic domain states at room temperature. However, when a storage site is heated (e.g. by laser light energy) to a temperature beyond a characteristic temperature, known as the Curie temperature, all memory of a prior magnetization polarity or state is lost. As this site cools to below the Curie temperature it assumes a magnetization state determined by a residual magnetic field, usually supplied by an external bias electromagnet. One example of an optical flying head having an external bias electromagnet is provided by commonly assigned U.S. Pat. No. 5,105,408 to Lee et al., entitled: xe2x80x9cOptical Head with Flying Lensxe2x80x9d, the disclosure thereof being incorporated herein by reference. In this prior approach the bias coil was formed as a printed microcircuit carried on a surface of the slider body facing the storage medium and having a central opening through which laser light energy passes from the lens While locating the coil in the manner described in U.S. Pat. No. 5,105,408 enables a field to be directed toward the storage site whose magnetic state is to be changed, the approach suffers from a number of drawbacks.
One drawback of this prior approach is that for a given driving current fully one half of the resultant magnetic field volume generated by the prior coil extended upwardly through the non-magnetic slider body and away from the storage medium. This condition uselessly added to the Amp*Turn requirement for a given magnetic field strength in the storage medium. Prior attempts at overcoming this drawback have been to provide multiple layers of thin-film coil windings, which adds further complexity and delicacy to an already complex and delicate manufacturing process. Another related drawback was that be cause the coil was inefficient in delivering flux at desired concentration to the storage medium, a higher driving current resulted in the generation of unwanted heat which results in undesirable thermal gradients within the head structure and may result in off-track operation of the optical drive mechanism. These drawbacks are overcome by the present invention.
One object of the present invention is to provide a layer of nickel-iron alloy material directly between the coil and the slider body which reduces magnetic reluctance and increases flux density directed toward the storage medium in ways overcoming limitations and drawbacks of the prior art.
Another object of the present invention is to enable production and usage of a simpler-to-produce single layer thin f bias coil structure within a flying head assembly.
A further object of the present invention is to improve the thermal transfer characteristics of an optical flying head assembly having a thin film bias coil structure.
In accordance with one aspect of the principles of the present invention, a flying optical head assembly is provided for an optical data storage system including a magneto-optical data storage medium. The assembly has a slider body flexibly suspended above said medium on an air bearing, and an optical element mounted to the slider body and having a narrowed optical aperture extending through a location of the slider body. The slider body defines a recessed region surrounding the location passing the optical aperture. A magnetic pole sheet layer is formed in the recessed region and has an insulation layer and an opening for the optical aperture; and, a generally spiral magnetic bias coil is formed on the insulation layer and surrounding the narrowed optical aperture. The magnetic pole sheet layer desirably reduces magnetic reluctance and results in greater flux concentration reaching the magneto-optical data storage medium. Also, the magnetic pole sheet layer may include a thermally conductive material and thereby serve as a heat sink and spreader which spreads heat otherwise generated at the optical aperture/bias coil location (either in the coil or due to media or lens heating by the laser beam) more effectively than heretofore.
In accordance with a second aspect of the principles of the present invention, a flying optical head assembly is provided for an optical data storage system including a magneto-optical data storage medium. The assembly includes a slider body flexibly suspended above said medium on an air bearing, and an optical element mounted to the slider body and having a narrowed optical aperture extending through a location of the slider body. The slider body defines a region of ferromagnetic pole material surrounding the location passing the optical aperture. A thermally conducting heat spreading structure is attached to the slider body at the region and has an insulation layer and an opening for the narrowed optical aperture. A generally spiral magnetic bias coil is fixed on the insulation layer and surrounds the narrowed optical aperture.
In accordance with a third aspect of the principles of the present invention, an optical disk drive data storage system includes a flying optical head assembly for flying over a data storage surface of a rotating magneto-optical data storage disk upon an air bearing, and also includes a voice coil actuator and suspension assembly for positioning the flying optical head radially relative to the data storage surface. The flying optical head assembly has a slider body flexibly suspended above the disk on an air bearing and supports an objective lens and a light-direction-changing mirror assembly. A solid immersion lens optical element is mounted to the slider body and has a narrowed optical mesa extending through a location of the slider body in general alignment with a light path formed by the mirror assembly and the objective lens and further has a surface generally coplanar with air bearing surfaces of the slider body. The slider body defines a recessed region surrounding the location passing the optical mesa. A multi-layer magnetic pole-providing and heat-spreading structure is formed in the recessed region and has an outer insulation layer surrounding an opening for the narrowed optical aperture. A generally spiral magnetic bias coil is patterned and deposited onto the insulation layer and surrounds the narrowed optical aperture. In this aspect of the invention the multi-layer magnetic pole-providing and heat-spreading structure preferably comprises a first layer of nickel-iron alloy, a second layer of copper alloy, and a third layer of nickel-iron alloy, and further comprises a series of circumferentiauly spaced apart radial slots defined in the structure, and further comprises a bonding agent present in each slot for bonding the magnetic pole-providing and heat-spreading structure to the slider body and for reducing eddy currents and a single-turn short in close proximity to the magnetic bias coil.